Cubic boron nitride is an abrasive designed for grinding, honing, lapping and polishing various substrates. It is bonded and formed into grinding wheels and other abrasive devices and surfaces of varying shapes, sizes and forms by means of a metal bond, an organic resin bond or by a vitreous bond. The abrasive is used most often in metalworking industries such as the automotive, bearing, cutting tool manufacturing, steel, fluid power, and gas turbine industries.
In any abrasive system friction is generated as a result of chip formation and sliding contact which, in the case of grinding, occurs at the abrasive crystal-workpiece interface, that is, at the point of contact between the abrasive substance and the substrate (workpiece) being ground, honed, lapped, polished or otherwise subjected to the action of the abrasive substance.
During such operations heat can cause premature bond failure, thermal stress failure of the abrasive and undue workpiece damage. It is well known that applying a lubricous and cooling fluid to the grinding wheel-workpiece interface during grinding operations can overcome these disadvantages.
For maximum cost effectiveness and grinding wheel life, grinding wheels containing cubic boron nitride abrasives require an adequate flow of properly selected fluids applied directly to the wheel-workpiece interface. Up to the present, water soluble oils, petroleum based oils, synthetic and semi-synthetic oils have been used as fluids in the operation of grinding wheels containing cubic boron nitride abrasives. Light duty soluble oils give satisfactory results. Even better results can be achieved through the use of heavy duty synthetic oils which contain extreme pressure (EP) additives. Such oils are widely applied to grinding wheels containing cubic boron nitride abrasives at a concentration of 1:20. Optimum results, however, are achieved with chlorosulfonated petroleum oils.
While optimum results can be achieved through the use of chlorosulfonated petroleum oils and petroleum based oils in general, there are certain disadvantages in their application as fluids for grinding wheels containing cubic boron nitride abrasives. One of the disadvantages in using the petroleum based oils is their flammability at the temperatures under which they operate. Typical flash point values for such oils will be between 280.degree. F. and 340.degree. F. Such oils have been known to ignite after being applied to the abrasive-workpiece interface. Another disadvantage in the use of petroleum based oils as fluids in the grinding process is the formation of toxic products in suspended mist form which result from the heating and breakdown of such petroleum oils during use. As a result of this there can be inherent health and safety hazards for individuals whose employment entails the operation of the above grinding wheels in conjunction with petroleum based fluids.
Accordingly, it is the primary object of this invention to overcome the foregoing disadvantages of the prior art fluids used to reduce frictional heat generated at the abrasive crystal-workpiece interface.
Another object of this invention is to provide a method which overcomes the safety and environmental hazards encountered in the use of petroleum based fluids in the operation of grinding wheels containing cubic boron nitride abrasives.
Another object of this invention is to provide a method which provides a grinding wheel life substantially the same as the grinding wheel life provided by methods employing prior art petroleum or synthetic based fluids while overcoming the disadvantages in the use of the petroleum based fluids.